Restricted-service automatic telephone system



Dec. 29,1925. 1,567,240

W. W. CARPENTER RESTRICTED SERVICE AUTOMATIC TELEPHONE SYSTEM Filed Oct. 11, 1923 2 Sheets-Sheet 1 /n en for: Warren W. (a/wen fer Y Aify.

Dec. 29 1925- W. W. CARPENTER 7 RESTRICTED SERVICE AUTOMATIC TELEPHONE SYSTEM Filed Oct. 11, 192: 2 Sheets-Sheet 2 r r k v h E Z. s mm S wxw W v m. JWM m W Cu d @m 5 W v6 m a uw h \Y \%\.H' !\\%N QN wfifimq Arr.

Patented Dec. 29, 1925.

UNITED stares Pier, 1115.'l l "OF F [C E GARPENTER,"OF"QUEFENS, NEVFY ORKJ ASSIGNOR T0 WESTERN ELECTRIC COMPANYQINCO RPORATED, OF NEW YORK,-N. Y., A CORPORATION OF NEW YORK.

RESTRICTEDSERVICE AUTOMATIC TELEPHONE SYSTEM.

Application filed October 11, 1923.

To all whom it may concern:

Be it known that LWVARBEN 1V. CARPEN- ran, a citizen of the United States, residing at Queens, in the county of Queens and State of New York, have invented certain new and useful Improvements in Restricted- Service Automatic Telephone Systems, of which the following is a full, clear, concise, and exact description.

This invention relatesto automatic telephone exchange'systems and more particularly to systems involving private branch exchange working.

Its object is to provide an improved circuit arrangement for restricted service lines; that is, lines from whichconnections can be set up automatically with other private branch "exchange lines, but when the outgoing or central'oflice trunk group is selected from such lines, busy tone is sent back to the subscriber attempting to' set up the prohibited connection.

In accordance with this invention, each connecting circuitis provided with a test relay which, when the calling line is automatically extendedto the connecting circuit upon the initiation of the call is connected to and'tests for an electrical condition on oneof the calling line terminals which condition is permanently applied only to lines of one class, for example, non-restrictedlines, and operates if such condr tion is present to control the electrical condition of: the test brush of the first selector to determine whether it will seize an idle trunk in the main-oflice level or pass over all the trunks in the level irrespective of their busy or idlecondition.v The operation of this relay on local trunk levels has no efiect on. the trunk hunting operation.

Referring to the drawings:

Fig. 1 .shows a calling subscribers line and an automatic linefinder switch and Fig. 2 shows a selector, a connect-or and the called line.

The line finder is of the Strowger stepby-step type and is equipped with twoba'nks and two sets of brushes,-'one hundred-lines terminatingin each bank. The lines-are in ten groups, corresponding to theten ver- Serial No. 667,796.

tical positions of the switch. Each group therefore contains twenty lines, ten in the upper and ten in thelower bank. "Every rotary position of the switch therefore embraces two lines of a group, one in theupper bank and one in the lower, and the connection is established with but one of thetwoyi. e., that one which is calling.

The invention will be most readily understoodfrom a detailed description of the operation.

The initiation of a call in line X or Y operates the corresponding line relay LR, LR. This causes the operation of group relay G. Relay G at its armature 166 grounds the start wire 100 and at its armature133 grounds commutator terminal 101 corresponding to the calling group. Relay A now operates as follows: ground, 160, 100, 168, 102, 103, A, battery. Relay A disconnects the brushes of the line finder from the tip and ring conductors 104, 105, to prevent interference and energizes the impulse relay A of the first selector (Fig. 2) as follows: ground, 100, 107, 120, 108, 109, 110, 111, 105, 201, A, battery. A operates slow-to-release relay'B, which inter-poses a break in the line finder release circuit and prepares the circuits of thefirst selector to receive the setting impulses. Relay A also starts the vertical hunting movement of the finder by operating relay C as follows: battery, 0, 112, 113, 114., 115, 116, 117, 118, 119, 120, 107, 106, ground. Relay C closes thefollowing circuit for the vertical magnet 121: battery, 121, 122, 123, 124., 125, 126, 127, 108, 107, 106, ground. The vertical magnet at the end of the stroke of its armature 114 opens the circuit traced forrelay C, which in releasing its armature 124, opens the circuit of the vertical magnet. This well known cycle continues until the group brush 128 reachesthe calling group commutator segment 101, and the ground on this segment holds the relay 0 energized over the following circuit and thus arrests the switc'hz-battery, C, 112, 113, left winding ofrelay: E, 129,139, 130, 131, 128, 101, 132,

-1 33,-.ground. Relay E, whichis slow to release, Y operates in 1 this circuit and locks as follows: battery, vertical magnet 121, 122, 125, 150, 151, 152, right winding of relay E, 127, 108, 120, 107, 106, ground. Relay E connects the commutator ground to the rotary magnet 134 to operate the same to rotate the brushes into the bank and begin testing the lines of the calling group of twenty lines. The circuit for said magnet 134 is as follows: battery, 134, 135, 136, 137, 133, 139, 130, 131, 123, 101, 132, 133, ground. Magnet 134 at the end of its stroke opens the circuit of relay C. The testterminals S, S of all lines are normally grounded at the right hand armatures 161, 147, etc. of their line relays. The upper and lower lines are tested simultaneously. If both are non-calling, ground on the upper test terminal S short circuits relay F at point 140 and operates relay C. The circuit for relay C is as follows: battery, 0, 112, 113, 114, 115, 155, 110, 156, 157, 158, 159, S, 160, 161, ground. Ground on the lower test terminal S short circuits relay D at point 141, and operates the rotary magnet 134 to move the brushes 01f these two non-calling lines. This circuit is as follows: battery, 134, 135,136, 111, 14.2, 14.3, 144, S, 145, 146, 147, ground. The rotary magnet on attracting its armature 154 locks itself to ground over 135, 136, 141, 137, 154, 118, 119, 120, 107, 106; and at the end of the stroke of its armature 113 opens the oi:- cuit of relay 0, which in releasing its armature opens the circuit of magnet 134. This cycle continues as long as grounded or noncalling terminals S, S are encountered by the finder sleeve brushes 159, 144. When a calling line is reached the test circuit acts as follows: Assuming S only is ungrounded, that is to say, line X is the calling line, relay C fails to operate since no ground is present on S, and therefore no circuit is closed for the rotary magnet 134 to the ground on sleeve multiple S and consequently the finder stops. The absence of ground on sleeve S causes relay F to operate as follows: battery, G, 112, 113, 114, 115, 155, 110, F, 162, 163, 164, 165, ground. Belay C is marginal and will not operate in this circuit.

When relay F operates a test circuit is closed to the calling line to determine whether it is restricted or non-restricted. This circuit is as follows: battery, A, 103, 174, 175, right winding of B, 176, 177, 172, to the tip terminal T of the calling. line. If the line is non-restricted a conductor 178, as shown in connection with line X, connects the normally grounded outer right armature of cut off relay CO to the said tip terminal. If restricted, this conductor is absent, as, for example, as-shown in connection with line Y. Relay B operates in :the case of line X and locks to ground at 165 by its left winding over its left conline relay LB, whichreleases the group relay (,2- and at its left armature locks itself to said ground. Relay LR is slow to release to give the relay CO time to operate and lock. Relay CO in removing ground from conductor 178 opens the circuit of relay A, which releases. Relay A in releasing restores the continuity of the tip and ring conductors 104, 105, and since relay D is inert, said conductors connect the tip and ring terminals TB, and consequently the calling line X to the first selector (Fig. 2). Relay B at armature 151 opens the locking circuit traced including the right winding of relay E, which thereupon releases.

Assuming now that line Y had called instead of line X, terminal S instead of S would have been ungrounded. Although relay C operates in this case due to ground on S, as described, and at its armature 136, connects the rotary magnet to terminal S, this magnet does not operate since no ground is present on terminal S. Owing to the absence of ground on S, there is no shunt about the brush shifting relay D, and it operates as follows: battery, rotary magnet 13 1, 135, 136, 137, 138, 139, 130, 131, 170,1), 171, 116,117, 113,119, 120, 107, 106, ground. The rotary magnet 134 will not operate in this circuit. Relay D in attracting its armature 158 opens the short cir- 'cuit described about relay F, which thereupon operates as described to connect relay A to the tip conductor in series with relay B to test for ground on the tip T of the calling line Y and not finding such ground relay A releases, which in turn releases relay E. Belay D at its innermost lower armature closes a locking circuit for itself including conductor 164 and the 01fnormal switch 165. At its armatures 172, 173, relay D connects the tip and ring conductors 104, 105 to the brushes resting on terminals T B and thus extends the call ing line Y to the first selector (Fig. 2).

If both lines X and Y are calling, the finder stops and preference is given to line X. In this case both sleeve terminals S and S are ungrounded. Due to S being ungrounded, G fails to operate, as described, and F operates instead just as in the case described where line X alone was calling. The other operations are the same as those described where line X alone was calling.

When the calling line is restricted, no

groundi iis connectect i to the -tip; terminal, as in -the 'icase of line fY. Belay'l3tl1ei'elo1'e fails to ioperate and relay 1 A} 'ilnmediately releases; applying grouud as" follows to operate cut-ofi relay OO; ground, 106, 187, 143 and its: front contact, relay: D being operated, 188, 144, S, 145, 189, 1 90,- U0, battery. Relay O'O operates to cut oil the line relay 1 LR and at its lett armature locks itself to said groundn In the caseota restricted "line in the row enga-ged'iiby the upper setot brushes, the circuit :for operating the cut otl relayiot such lineid'oes not lead' iover the front contact 01 relay 18,: as described"ator dine 91, since in such "caserirelay' B is not *operatech' but the circuit is aasl-iollows z ground, 106, 187, 169, 156," 157, 158': and its hack-contact, Db'eing inert; 159;S, tohb'attery through the 'cut off relay of thatrline.

In the ease of ZtiillOIFl'EStl'lCtGdline in the inowv'engaged bythe lower set ot brushes, the: eircuiti'for operating the cut=odrelay .ofsuch line. does not dead over the back contact of relay -'=A,; as described 5 ton. line 13?, since nine rsuch -ca se' relay Be is operatecL- but the yeircuit JElS as ifol-lows: aground at "the 'ihackircontaetof release 1nagnet'192, inner right; armaturee and 1' front contact en relay .l5,l18.4,::169,: :143Eandwits1 front contaet,-t relay D being operated, 188,144, sfito battery Vthroughlthec'cuteofi relay of 1 such line.

dhssuming the line connected to hy the ilinder to 'lDB'llhne.EX,?IiEh(-3F.1IIIP1I1SBf'leltly "11 "EDCLNSIOW relay Boofi the firsttselector were --operated Wlhen; relay "A 'Was'roperated onthe initiatioin ofxthe' "call, --as described. i Wh'en relay. unreleased, the impulse relay Was held :energiizedvover line X by the-continuity eon- 'tactsmfi relay aA. Relay Al nowifollowsi the :d'i a-l impulses from line 5X; and' eaeln time it .releases,1groundfrom- .thei-upperinostr armatureiand: back contact of -relay; D"iislapplied 1:170? operateithe i velti'eal'rlnagnet 202 7111 series :withz slowirela- T G' WlfiCh remains-ener ized l/ a k:

during the "impulses. The vertical-- magnet steps theubrushes203,1:209, 207120 the proper level. i'Qn the first *vertieal'ste aythesolinonmal' switch. 204:) is joperateduand relay/ E is; energized oven the attenuate Contact of relay Cto: prepare the rotary steppingieircuit' zintthe' Well known manner. 1 After! the completion ofridialiing, relay 0'? releases :but relay :E remains locked "up cover its a'left armature, to ground at the uppermost anmaturei andrnormal .cotrtactcot relay D. 'Re'lay .C': in releasing closes a circuitnthrouglr the night armaturei and zalternate contact of relay LE to operate? the rotary magnet, which steps the :brushes 203 ionto ithe first trunk terminals 206, 210,208, and by unlocking relay-FE" lSHllISBlf deenergized. Ifathis trunk is busy, ritsasleeve terminal 208 .is grounded, awvhieh ashuntsi relay: D and:reoperateserrelay E- 111:.1'1116' wellaknown manner. 'llhemotary magnet :isiagainoperated and the operations just described areu'epeated until an idle trunk is found, which, having an ungrounded sleeve,relay D is unshunted and operates in series 'with relay E in the Well known manner, the latterremaining inert due to itsmlarginal adjustment. Relay D closes the talking circuit andsleeve circuit through to the brushes 203,209,207, and cuts on" relay A. Relay -D is now locked to the sleeve terminaly which is held grounded from the connector in the Well known 1110111161. It all trunks' are busy the brushes are stepped to the "eleventh position and a set of cum springs 211' operates and substitutes busy tone from source BT for the ground on the Winding of relay A applied through the secondary of dial tone source DT. Source DT is connected to the line as soon relay A in the"line'finder operates; to inform the subscriberthe circuits are ready fol-dialing.

When the calling line is refused connections on certain levels of the selectorgthe 'groundiheretofore referred to'applied to conductor 180, is extended-"by switch 213' closed on'these' levels bythe switch shaft to the test brush 207, and this results in the selector operating as though it found all the trunks inlthis-ley'el busy, and'returns a busy signal to 'the 1 calling party from the all trunks busy source 'BJT.

Where the selector brushes 203, "209, 207 pick 1 out an idle connector, the impulse relay 214 thereof is operated to-set the same on the desired line in the well known manner. I

Ba'ttery for talking purposes is fed to the ca lling linethrough it relay 214 and to the called line I through relay 215.

Therelease is controlled by the calling party, and upon his replacing the receiver, relay 214 releases and removes holding ground from thesleeye Wire, which releases the connector in the Well known i'i'ianner. The removal of this ground, by rcleasi 11;: relay D,-oloses the circuit ol release nmgnet 216 i11the Well known manner to restore the selector.

The linc finder is'released by the ground applied jto release control conductor 191 due to the release of relay D. "This ground is ra 'iplied over the uppermost armature of relay D, armatures andhack contacts oi rclays B, A, conductor 191, oll-normal switch 165, to the left Winding of relayB tof battery in the case of a restricted line. such as Y. If the calling line isnonrestricted, relay B is locked at this time to oilnorn'ial switch 165. Relay B locks to ground atiotf normal switch 165, and at itsinncr leftarn'iature applies the ground on concluc- :tor 191ito"relay A. Relay A disconnects the talking brushes from the trunk during release to prevent interference, and closes the ifollowingicircuitto the release magnet 192: ibatteiy 11 92, 151, (150.1125, 126,1127,108,i 120,

107, 106, ground. The release magnet armature applies ground to conductor 164 to close a second locking circuit for the left winding of relay 18 independently ofground at 165 and this ground also closes a second circuit for relay F to hold the same operated independently of its energizing circuit traced to ground at ofi normal switch 165. When the shaft restores, cit-normal switch 165 by opening its uppermost contact restores relay A. Relay A in releasing opens the ciron it of the release magnet. The release magnet in retracting its armature opens the I locking circuit of relay B. The retraction multipled to a jack 197 before an operator,

who may extend calls to the line by the plug 198. When a connection is made to the line at either set of multiples, the cutoff relay CO operates to cut oi the line relay LR to prevent starting a finder upon the response of the called party.

hat is claimed is:

1. In a telephone system, telephone lines of different classes, means for establishing difierent electrical conditions on the termi-,

nals of one of the talking conductors of certain of said classes of lines, selectors having groups of trunks, means automatically operated upon the closure of the calling line for extending the line to an idle selector, means controlled by the calling party for setting said selector to any trimk group, means thereupon automatically opera-ted for driving the selector over the trunk group, a switch closed by the selector when set to a certain group, and means jointly controlled by the electrical condition of the calling line terminal and said switch for determining whether the selector shall select an idle trunk or pass over idle trunks when set to the said group.

2. In a telephone system, telephone lines of different classes, means for establishing difierent electrical conditions on the terminals of one of the talking conductors of certain of said classes of lines, selectors having groups of trunks, means automatically operated upon the closure of the calling line for extending the line to an idle selector, means controlled by the calling party for setting said selector to any trunk group,

means thereupon automatically operated for driving the selector over the trunk group, a switch closed by the selectorwhen set to a certain group, means jointly controlled by Y the electrical condition of the calling line terminal and said. switch for determining whether the selector shall select an idle trunk or pass over idle trunks when set to said group, and means operated at the end of the travel of the selector for transmitting a tone to the calling party. 1

3. In a telephone system, telephone lines of different classes, means for establishing different electrical conditions on the terminals of said classes of lines, selectors having groups of trunks, means automatically operated upon the closure of the calling line for extending the line to an idle selector, means controlled by the calling party for setting said selector to any trunk group, means thereupon automatically operated for driving the selector over the trunk group, a ground connection, a switch closed by the selector when set to a certain group to connect said ground to the selector test brush, means in said selector actuated by the presence of said connection for preventing the selector from seizing an idle trunk when set to said group, and a relay operated only on a call from one class of lines for preventing the extension of said ground connection when said switch is actuated.

4. In a telephone system, restricted lines, non-restricted lines, selectors having trunk groups, a finder for automatically extending a calling line to an idle selector upon the closure of the calling line circuit, each nonrestricted line having a terminal therein connected to one pole of the battery and the corresponding terminal of the restricted lines being disconnected from battery, a relay associated with the finder and operated only when the finder extends a non-restricted line, means for setting said selector to any trunk group and for automatically driving the same thereover, a ground connection, a switch closed by the selector on a given level to extend said ground to the selector test brush, means in said selector actuatedby the presence of said ground connection for preventing the selector from seizing an idle trunk when set to said'group, and a relay operated only on a call from non-restricted lines for preventing the extension of said ground connection when said switchis actuated.

5. In a telephone system, restricted lines,

non-restricted lines, selectors having trunk I terminal is ungrounded, a switch closed by with the finder and operated when a nonthe selector when set to a given level, a restricted line is extended for preventing l0 ground connection applied to the selector said switch from extending said ground contest brush by Way of said switch when said nection to said test brush, and a locking cirlevel is selected for applying ground to the cuit for said relay.

test terminals in said level as the selector In witness whereof, I hereunto subscribe passes over them to prevent any trunk theremy name this 3rd day of October, A. D. 1923.

in from being seized a test relay associated \VARREN W. CARPENTER. 

